Animal fibers are unique in that, depending on the type of fiber, they have a characteristic texture, are biodegradable, exhibit excellent moisture absorbing, moisture releasing, heat retaining, flame retarding, and dyeing properties, and further have water repelling properties. In terms of physical properties, animal fibers have fiber strength and elongation characteristics sufficient for being worn and also exhibit high frictional strength, and thus are unique fibers that have been valued since ancient times. However, felting that occurs due to the epidermal tissue structure of an animal fiber when the fiber is washed, and pilling that occurs when an animal fiber is worn, are not desirable characteristics of fiber for use in garments. Accordingly, efforts have long been made to modify the surface, focusing mainly on shrink proofing, and in association with this an anti-pilling treatment has been carried out as well.
However, water repellence, a natural feature of animal fiber, is sacrificed in animal fiber obtained in such a manner. The water repellent membrane in an animal fiber influences moisture absorbing and moisture releasing properties, functions to control heat transfer associated with the adsorption and desorption of water, and affects heat retention and comfort. In other words, conventional shrink resistant products can prevent shrinking resulting from washing but lack heat retention and comfort.
An example of a typical conventional shrink proofing method is a shrink proofing method that uses a chlorine agent in which the epidermal tissue of an animal fiber is made hydrophilic to soften or remove the tissue so as to give shrink resistance and, moreover, the epidermal tissue is coated with a polyamide epichlorohydrin resin (manufactured by Dick Hercules Co., Hercosett resin) to enhance washing resistance, i.e., the chlorine/Hercosett shrink proofing method. This method is currently in widespread use all over the world and arguably is regarded as the standard shrink proofing process for wool.
The applicants proposed shrink proofing that uses ozone in the following patent documents 1 to 2 as an alternative to the chlorine/Hercosett shrink proofing process.